The present invention relates to an apparatus for adjusting a difference in rotational phase between first and second rotary members, particularly suitable for adjusting an opening and closing timing of an intake valve or exhaust valve driven by a crank shaft through a cam shaft in an internal combustion engine.
In prior art cam shaft phase adjustors for internal combustion engines as disclosed by JP-A-6-10964, JP-A-6-10965 and JP-A-6-10966, an engagement between a first rotary member driven by a crank shaft and a second rotary member fixed to a cam shaft can be selectively released to adjust a difference in rotational phase between the crank shaft and the cam shaft, by a plunger moved by an electromagnetic or hydraulic actuator.